1. Technical Field
The present invention relates to equipment and methods used in subterranean wells, and more particularly, to apparatus for expanding liner hangers.
2. Background Art
In the process of drilling and completing hydrocarbon wells, it is common place to use heavy steel casing in a well and to place cement between the casing and the well to anchor the casing in place and prevent migration of fluids along the annulus outside the casing. After an upper portion of a well has been drilled and casing is cemented in place, it is common to resume drilling the well and install a liner in the lower part of the well by lowering the liner through the upper-cased portion of the well. Liner hangers are used to mechanically support the upper end of the liner at the lower end of the previously set casing and to seal the liner to the casing. Liner hangers have included slips for mechanical support and packers for forming a seal.
In addition, liner hangers that can be expanded against the wall of the previously set casing, such as those sold under the trademark VERSAFLEX®, by Halliburton Energy Services, have been developed. Expandable liner hangers provide both mechanical support and a fluid seal by use of a number of elastomeric rings carried on a section of expandable liner. In operation, the liner hanger is properly positioned in a cased portion of a well, and an expansion device is forced through the liner hanger to expand the liner hanger into the casing wall, compressing the elastomeric seals to provide both mechanical support and a fluid seal.
Systems for expanding liner hangers, such as, disclosed in U.S. Pat. No. 7,779,910, include an expansion cone having a first outer diameter when driven through the expandable liner hanger in a first direction to expand the expandable portion of the liner. The expandable liner hanger system also includes at least one piston to force the cone through the expandable portion of the liner hanger. The expansion process involves supplying pressure to the pistons.
Current liner expansion practice involves stroking the pistons approximately between 40 to 60 inches with a single surface pressure application. While effective, this method requires multiple pistons, each having a stroke length sufficient to move the cone the required expansion distance as well as additional distance for manipulation in the case of incomplete expansion. However, industry trends are moving toward heavier weight casing and higher pressures, which all act to increase the number of pistons required in the setting tool which, in turn, increases the length, handling, weight, and complexity of the setting tool. In some cases, even taking the pumping equipment to their pressure limits cannot effectively expand these heavier liners.